Environmental Engineering Reference
In-Depth Information
Plate 4.5
A section through the centre of a large hailstone,
taken in reflected light, showing regions of clear ice which
appear black and milky or opaque ice which appears white.
Photo: courtesy of Dr K. A. Browning.
freeze. Air bubbles can escape, leaving a layer of clear ice when it eventually freezes.
The alternating layers of clear and opaque ice indicate the number of times the hailstone
has been swept up by the cloud updraughts.
CONVERGENT PRECIPITATION
In temperate and subpolar latitudes most of the precipitation comes from depressions.
They are characterized by areas of rising air associated with convergence. A satellite
photograph of a cyclone shows the extensive areas of cloud resulting from this slow but
widespread ascent of the air (Plate 4.6).
